Headphone

ABSTRACT

A headphone includes an electro-acoustic transducer for creating audio output, the electro-acoustic transducer comprising a transducer magnet that produces a transducer magnetic field having a magnetic field strength, a housing constructed and arranged to be positioned at an ear of a wearer so as to direct the audio output at the ear canal of the ear, a magnetic field sensor positioned in the housing and constructed and arranged to sense the Earth&#39;s magnetic field, and a nulling magnet positioned in the housing and constructed and arranged to produce a nulling magnetic field that reduces the strength of the transducer magnetic field at the magnetic field sensor.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority of applicationSer. No. 15/913,143 filed on Mar. 6, 2018.

BACKGROUND

This disclosure relates to headphones.

Earphones (e.g., earbuds or headphones) can include orientation trackingsystems that use a magnetometer to track motions of the head and thedirection in which the wearer is looking. Magnetometers need toaccurately detect the Earth's magnetic field. The earphone'selectro-acoustic transducer typically includes a magnet. Since someearphones, such as in-ear headphones (sometimes also called earbuds) aredesirably quite small, of necessity the magnetometer is close to themagnet of the transducer. The magnetic field of the transducer magnettypically has a magnetic field strength that is much greater than theEarth's magnetic field. Accordingly, the transducer's magnetic field canoverwhelm the magnetometer and prevent it from working properly.

SUMMARY

All examples and features mentioned below can be combined in anytechnically possible way.

In one aspect, a headphone includes an electro-acoustic transducer forcreating audio output, the electro-acoustic transducer comprising atransducer magnet that produces a transducer magnetic field having amagnetic field strength, a housing constructed and arranged to bepositioned at an ear of a wearer so as to direct the audio output at theear canal of the ear, a magnetic field sensor positioned in the housingand constructed and arranged to sense the Earth's magnetic field, and anulling magnet positioned in the housing and constructed and arranged toproduce a nulling magnetic field that reduces the strength of thetransducer magnetic field at the magnetic field sensor.

Embodiments may include one of the following features, or anycombination thereof. The magnetic field sensor may comprise a three-axismagnetometer. The nulling magnet may comprise a permanent magnet. Thenulling magnet may comprise an electromagnet.

Embodiments may include one of the above and/or below features, or anycombination thereof. The electro-acoustic transducer may comprise amagnetic structure that comprises the transducer magnet and magneticmaterial that guides the transducer magnetic field. The magneticstructure may span a magnetic structure distance, and the magnetic fieldsensor may be located within a distance from the magnetic structure thatis no greater than the magnetic structure distance. The headphone mayfurther comprise an additional magnet that is spaced from the magneticstructure by an inter-magnet distance. The magnetic field sensor may belocated within a distance from both the magnetic structure and theadditional magnet that is no greater than the inter-magnet distance. Theheadphone may comprise an earbud and the housing may comprise an earbudbody, and the magnetic structure and the additional magnet may both belocated within the earbud body. The additional magnet may comprise acoupling magnet for coupling the earbud to another structure.

Embodiments may include one of the above and/or below features, or anycombination thereof. The headphone may comprise an earbud, and thehousing may comprise an earbud body. The magnetic field sensor may havea sensed magnetic field range where it operates linearly, and thenulling magnetic field may reduce the strength of the transducermagnetic field at the magnetic field sensor such that the sensedmagnetic field strength is in the sensed magnetic field range where themagnetic field sensor operates linearly. The transducer magnetic fieldstrength at the position of the magnetic field sensor may be at least100 μT. The magnetic field sensor may be positioned less than 10 mm fromthe electro-acoustic transducer. The transducer magnet may have adiameter of about 8 mm.

In another aspect, an earbud includes an electro-acoustic transducer forcreating audio output, the electro-acoustic transducer comprising atransducer magnet that produces a transducer magnetic field having amagnetic field strength, an earbud body constructed and arranged to bepositioned at an ear of a wearer so as to direct the audio output at theear canal of the ear, a three-axis magnetometer positioned in the earbudbody and constructed and arranged to sense the Earth's magnetic field,and a nulling permanent magnet positioned in the earbud body andconstructed and arranged to produce a nulling magnetic field thatreduces the strength of the transducer magnetic field at the three-axismagnetometer. The three-axis magnetometer has a sensed magnetic fieldrange where it operates linearly, and the nulling magnetic field reducesthe strength of the transducer magnetic field at the three-axismagnetometer such that the sensed magnetic field strength is in thesensed magnetic field range where the three-axis magnetometer operateslinearly.

Embodiments may include one of the above and/or below features, or anycombination thereof. The electro-acoustic transducer may comprise amagnetic structure that comprises the transducer magnet and magneticmaterial that guides the transducer magnetic field, wherein the magneticstructure spans a magnetic structure distance, and wherein thethree-axis magnetometer is located within a distance from the magneticstructure that is no greater than the magnetic structure distance. Thetransducer magnet may have a diameter of about 8 mm and the three-axismagnetometer may be positioned less than 10 mm from the electro-acoustictransducer. The transducer magnetic field strength at the position ofthe three-axis magnetometer may be at least 100 μT. The earbud mayfurther comprise a coupling magnet positioned within the earbud body andadapted to couple the earbud to another structure, wherein the couplingmagnet is spaced from the magnetic structure by an inter-magnetdistance, and wherein the magnetic field sensor is located within adistance from both the magnetic structure and the coupling magnet thatis no greater than the inter-magnet distance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is perspective view of an in-ear headphone.

FIG. 2 is a partial cross-sectional view of elements of an in-earheadphone.

FIG. 3 is a schematic view of the magnetic structure of an in-earheadphone and its magnetic field at the location of a magnetic fieldsensor.

FIG. 4 is a view similar to that of FIG. 3 but including a nullingmagnet.

FIG. 5 is a schematic diagram of an in-ear headphone.

DETAILED DESCRIPTION

In a headphone with an electro-acoustic transducer magnet and amagnetometer that is located close to the transducer, the transducer'smagnetic field can overwhelm the magnetometer and prevent it fromproperly detecting the strength of the Earth's magnetic field. Themagnetometer can be brought into a region of stable operation with anadditional nulling magnet located such that its magnetic field partiallyor fully nulls the transducer magnetic field at the location of themagnetometer, sufficiently such that the magnetometer can operate in itslinear operational region where stray magnetic fields do not overwhelmthe Earth's magnetic field.

FIG. 1 is a perspective view of in-ear headphone or earbud 10. Earbud 10includes body 12 that houses the active components of the earbud.Portion 14 is coupled to body 12 and is pliable so that it can beinserted into the ear canal. Sound is delivered through opening 15.Retaining loop 16 is constructed and arranged to be positioned in theouter ear, for example in the antihelix, to help retain the earbud inthe ear. Earbuds are well known in the field (e.g., as disclosed in U.S.Pat. No. 9,854,345, the disclosure of which is incorporated herein byreference), and so certain details of the earbud are not furtherdescribed herein. An earbud is an example of a headphone according tothis disclosure, but is not limiting of the scope, as headphones canalso be located on or over the ear, or even on the head near the ear.

FIG. 2 is a partial cross-sectional view of only certain elements ofin-ear headphone 20 that are useful to a better understanding of thepresent disclosure. Headphone 20 comprises housing 21 that encloseselectro-acoustic transducer 30. Housing 21 comprises front housingportion 50 and rear housing portions 60 and 62. Transducer 30 hasdiaphragm 32 that is driven in order to create sound pressure in frontcavity 52. Sound pressure is directed out of front housing portion 50via opening 54. When headphone 20 is an earbud, as shown in FIG. 1,there is typically a pliable tip that is engaged with neck 51 of housingportion 50, to direct the sound into the ear canal. In-ear headphonehousing 21 further comprises a rear enclosure made from rear housingportions 60 and 62, and grille 64.

Transducer 30 further comprises magnetic structure 34. Magneticstructure 34 comprises transducer magnet 38 and magnetic material thatfunctions to confine and guide the magnetic field from magnet 38, sothat the field properly interacts with coil 33 to drive diaphragm 32, asis well known in the electro-acoustic transducer field. The magneticmaterial comprises cup 36 and front plate 35, both of which arepreferably made from a material with relatively high magneticsusceptibility, also as is known in the field. Transducer printedcircuit board (PCB) 40 carries electrical and electronic components thatare involved in driving the transducer. Pads 41 and 42 are locationswhere wires (not shown) can be coupled to PCB 40.

Three-axis magnetometer 72 is mounted on PCB 70 and is arranged to sensethe strength of magnetic fields in three axes at the location of themagnetometer, as is known in the field. Magnetometer 72 is configured todetect the Earth's magnetic field. The output of magnetometer 72 can beused, to determine the direction in which the wearer's head is pointed,as described in U.S. Patent Application 62/626,967, filed on Feb. 6,2018, the entire disclosure of which is incorporated herein byreference.

Since magnetometer 72 is close to transducer magnet 38, the transducer'smagnetic field can overwhelm the magnetometer and prevent it fromproperly detecting the strength of the Earth's magnetic field. Themagnetometer can be brought into its specified measurement range (wherestray magnetic fields do not skew the desired measurement) with anadditional nulling magnet 74. Nulling magnet 74 is located such that itsmagnetic field partially or fully nulls the transducer magnetic field atthe location of magnetometer 72. This field nulling should take place inany one, two, or three of the three axes in which stable operation ofthe magnetometer is needed. In the present case, stable magnetometerresults are desired in all three axes, so the nulling magnet isconfigured to sufficiently null the Earth's magnetic field in all threeaxes. It should be understood that the location of nulling magnet 74 inFIG. 2 is representative, and magnet 74 may actually be locatedelsewhere in housing 21. It should also be understood that magnet 74could be a permanent magnet or an electromagnet, it being necessary onlyto properly place and orient a nulling magnetic field, as describedelsewhere herein. The nulling should be sufficient such thatmagnetometer 72 can operate in its linear operational region where straymagnetic fields do not overwhelm the Earth's magnetic field. Linearoperation of magnetometers (where there are stray magnetic fields thatare not so strong that they overwhelm sensing or detection of thedesired field) is known in the technical field, and so is not furtherdescribed herein.

FIGS. 3 and 4 illustrate aspects of an in-ear headphone. In-earheadphone electro-acoustic transducer 80 comprises magnet 82, and amagnetic structure 85 that comprises cup 86 and front member 84. Magnet82 has a magnetic field, which is represented by the generally verticalfield line representations 83. In one illustrative, non-limitingexample, magnet 82 has a magnetic field strength of up to about 3000 μT.Magnetic fields and field line representations are well known in the artand so are not further described herein. The magnetic structure 85 spansa distance “d.” Magnetometer 90 is spaced a distance “d′” from magneticstructure 85. The field from magnet 83 in the vicinity of magnetometer90 is represented by field lines 92. In the example, the field strengthof the magnetic field from magnet 82 in the vicinity of magnetometer 90is about 500 μT; this is less than 3000 μT in part due to the distanceof the magnetometer from the magnet, and in part due to the partialshielding of the magnetic field by magnetic structure 85. In contrast,the strength of the Earth's magnetic field is generally approximately 50μT, or about 1/10^(th) of the field from magnet 82. With a stray fieldsuch as this that overwhelms the field to be sensed, magnetometer 90will be inaccurate. Accordingly, the look direction sensing involvingmagnetometer 90 will be inaccurate. It should be understood thatelectro-acoustic magnet transducers can have varied shapes, sizes,locations, and field strengths, and that the illustrative values setforth in the examples are not limiting of the scope of this disclosure.

FIG. 4 illustrates schematically an effect of nulling magnet 94. Nullingmagnet 94 has a magnetic field, which is represented by the generallyvertical field line representations 95. Nulling magnet 94 has a size,shape, magnetic orientation, magnetic field strength, and locationrelative to transducer 80 and magnetometer 90 such that its magneticfield is superimposed on the field from the transducer magnet 82sufficiently to fully or partially null the transducer field in threeaxes, at the location of magnetometer 90. In this non-limiting example,field nulling is indicated by field line representation 92 a, showing afield null at magnetometer 90 (i.e., no field lines intersectmagnetometer 90). It should be understood that the field does not needto be fully nulled by nulling magnet 94. Rather, as described above, thestrength of the field needs to be reduced sufficiently such that themagnetometer can sense the Earth's magnetic field. The reduction in thetransducer field at the magnetometer that needs to be accomplished withthe nulling magnet will in part depend on the particular magnetometerused, as would be apparent to one skilled in the field. Also, it shouldbe understood that magnetic fields are three-dimensional, while FIGS. 3and 4 are two-dimensional. Those skilled in the field will understandthe extent to which the transducer magnet's field in three dimensionsneeds to be nulled in order for the sensing of the Earth's magneticfield to be accomplished with sufficient accuracy for the particularapplication of the Earth's magnetic field sensor, and can make anappropriate selection of the nulling magnet parameters described aboveto accomplish such results.

In one non-limiting example, transducer magnet 82 can be a generallycylindrical magnet with a diameter of about 8 mm, and cup 86 can have adiameter d of about 10 mm. In one non-limiting example, sensor 90 can bepositioned less than about 10 mm (distance d′) from transducer 80. Inone non-limiting example, the magnetic field strength of the transducermagnet at sensor 90 is at least about 100 μT.

FIG. 5 is a schematic diagram of in-ear headphone 100, illustrating inpart an exemplary placement of magnetic field sensor 108 relative totransducer 104 and an additional magnet 106. Battery 114 provides powerto powered components. Processor 112 is used, in part, to drivetransducer 104 and determine the wearer's look direction, in part usingthe output of magnetic field sensor 108. It should be understood thatin-ear headphones will have more components and can have differentcomponents than those shown in FIG. 5. Some in-ear headphones include amagnet other than the transducer magnet. This other or additional magnetis represented in this non-limiting example by coupling magnet 106.Coupling magnet 106 can be used to couple headphone 100 to anotherstructure. As one non-limiting example, magnet 106 can be used to dockor “park” an earbud to a neckband or a battery charger. Other uses ofparking magnets are known in the field and are included within the scopeof the present disclosure.

All of the magnets in earbud body 102 of headphone 100 create magneticfields that can adversely impact the accuracy of the sensing of theEarth's magnetic field by sensor 108, as described above. In oneexample, the distance spanned by the earphone's magnetic structure 103(comprising all of the magnets and magnetic material in theelectro-acoustic transducer 104 together with the additional (coupling)magnet 106) is defined as d″. D″ can alternatively be defined as theinter-magnet distance. It is believed that when sensor 108 (which islocated a distance d′″ from magnetic structure 103) is within a distanceequal to d″ of magnetic structure 103, sensor 108 is in danger of beingoverwhelmed by the stray magnetic fields from magnetic structure 103. Inother words, if d′″ is less than or equal to d″, there is a potentialproblem. Alternatively, a potential problem can be determined bymeasuring stray magnetic fields at the location of the magnetometer. Ifthe stray fields are too large for the magnetometer to handle, nullingmagnet 110 is used to sufficiently null the stray magnetic fields, asdescribed above.

Elements of FIG. 5 are shown and described as discrete elements in ablock diagram. These may be implemented as one or more of analogcircuitry or digital circuitry. Alternatively, or additionally, they maybe implemented with one or more microprocessors executing softwareinstructions. The software instructions can include digital signalprocessing instructions. Operations may be performed by analog circuitryor by a microprocessor executing software that performs the equivalentof the analog operation. Signal lines may be implemented as discreteanalog or digital signal lines, as a discrete digital signal line withappropriate signal processing that is able to process separate signals,and/or as elements of a wireless communication system.

When processes are represented or implied in the block diagram, thesteps may be performed by one element or a plurality of elements. Thesteps may be performed together or at different times. The elements thatperform the activities may be physically the same or proximate oneanother, or may be physically separate. One element may perform theactions of more than one block. Audio signals may be encoded or not, andmay be transmitted in either digital or analog form. Conventional audiosignal processing equipment and operations are in some cases omittedfrom the drawing.

The example of FIG. 5 comprises a processor that is configured to usecomputer-implemented steps that will be apparent to those skilled in theart. For example, it should be understood by one of skill in the artthat the computer-implemented steps may be stored as computer-executableinstructions on a computer-readable medium such as, for example, floppydisks, hard disks, optical disks, Flash ROMS, nonvolatile ROM, and RAM.Furthermore, it should be understood by one of skill in the art that thecomputer-executable instructions may be executed on a variety ofprocessors such as, for example, microprocessors, digital signalprocessors, gate arrays, etc. For ease of exposition, not every step orelement of the systems and methods described above is described hereinas part of a computer system, but those skilled in the art willrecognize that each step or element may have a corresponding computersystem or software component. Such computer system and/or softwarecomponents are therefore enabled by describing their corresponding stepsor elements (that is, their functionality), and are within the scope ofthe disclosure.

A number of implementations have been described. Nevertheless, it willbe understood that additional modifications may be made withoutdeparting from the scope of the inventive concepts described herein,and, accordingly, other embodiments are within the scope of thefollowing claims.

What is claimed is:
 1. An earphone, comprising: a magnetic field sensorthat is constructed and arranged to sense the Earth's magnetic field; afirst magnet that produces a first magnetic field having a firstmagnetic field strength; and a nulling magnet that produces a secondmagnetic field that is configured to reduce an influence of the firstmagnetic field on the magnetic field sensor.
 2. The earphone of claim 1,wherein the magnetic field sensor comprises a magnetometer.
 3. Theearphone of claim 1, wherein the magnetic field sensor comprises athree-axis magnetometer.
 4. The earphone of claim 1, wherein the nullingmagnet comprises a permanent magnet.
 5. The earphone of claim 1, whereinthe first magnet comprises a transducer magnet of an electro-acoustictransducer that is adapted to create an audio output.
 6. The earphone ofclaim 5, further comprising a housing that is constructed and arrangedto be positioned at an ear of a wearer so as to direct the audio outputat the ear canal of the ear.
 7. The earphone of claim 6, wherein thenulling magnet is positioned in the housing such that the secondmagnetic field reduces the strength of the transducer magnetic field atthe magnetic field sensor.
 8. The earphone of claim 5, wherein theelectro-acoustic transducer comprises a magnetic structure thatcomprises the transducer magnet and magnetic material that guides thetransducer magnetic field.
 9. The earphone of claim 1, wherein theearphone comprises an earbud with an earbud body, and wherein themagnetic field sensor, the first magnet, and the nulling magnet are alllocated in the earbud body.
 10. The earphone of claim 1, wherein themagnetic field sensor has a sensed magnetic field range where itoperates linearly, and wherein the second magnetic field reduces thestrength of the first magnetic field at the magnetic field sensor suchthat the sensed magnetic field strength is in the sensed magnetic fieldrange where the magnetic field sensor operates linearly.
 11. Theearphone of claim 1, wherein the first magnetic field strength at theposition of the magnetic field sensor is at least 100 μT.
 12. Theearphone of claim 1, wherein the magnetic field sensor is positionedless than 10 mm from the first magnet.
 13. The earphone of claim 12,wherein the first magnet has a diameter of about 8 mm.
 14. An earbud,comprising: an electro-acoustic transducer for creating audio output,the electro-acoustic transducer comprising a transducer magnet thatproduces a transducer magnetic field having a magnetic field strength; amagnetometer constructed and arranged to sense the Earth's magneticfield; and a nulling magnet constructed and arranged to produce anulling magnetic field that reduces the strength of the transducermagnetic field at the magnetometer.
 15. The earbud of claim 14, whereinthe magnetometer has a sensed magnetic field range where it operateslinearly, and wherein the nulling magnetic field reduces the strength ofthe transducer magnetic field at the magnetometer such that the sensedmagnetic field strength is in the sensed magnetic field range where themagnetometer operates linearly.
 16. The earbud of claim 14, wherein thetransducer magnet has a diameter of about 8 mm and the magnetometer ispositioned less than 10 mm from the electro-acoustic transducer.
 17. Theearbud of claim 15, wherein the transducer magnetic field strength atthe position of the magnetometer is at least 100 μT.
 18. The earbud ofclaim 14, wherein the magnetometer comprises a three-axis magnetometer.19. The earbud of claim 14, wherein the nulling magnet comprises apermanent magnet.
 20. The earbud of claim 14, further comprising anearbud housing, and wherein the electro-acoustic transducer,magnetometer, and nulling magnet are all located in the earbud housing.